Thin film semiconductor materials form the basis for electronics industry from which many commonly used devices and popular technologies are generated. For example, semiconductors are needed to make transistors and memory chips used in computers and cell phones, they are used to generate energy from the sun via photovoltaic effects or from heat via thermoelectric effects, they can be used to catalyze chemical reactions, and are also essential to create display technologies. Ongoing efforts are underway across the industry to provide new semiconductor materials having improved performance while easier and less expensive to make. In particular, semiconductors having amorphous crystal structures are sought because they can be fabricated cheaply over large areas.
Among the available amorphous semiconductor materials only ZnO or SnO2 doped with other materials such as In, Ga, Al, etc. have found application in technologies such as touch screen and active matrix displays. This is partly due to the need for a combination of requirements such as optical transparency, low processing temperatures, stability, good semiconductor performance and low material cost. Among these materials, Indium metal is the basis for a number of the high performing amorphous oxide semiconductors (e.g. In—Ga—Zn—O or IGZO) requiring high carrier hall mobility (>10 cm2/V-s) in amorphous state. However, Indium is a precious metal; its low earth abundance is detrimental to its usage. There is a need to alleviate difficulties such as the scarcity of indium.
Among available amorphous semiconductor materials, none have shown the ability to combine ferromagnetism at room temperature along with transparency and semiconductor behavior. Such a material could help advance technology and applications pertaining to control of the spin of charge carriers, such as used in spintronic devices, the most popular example being the giant magnetoresistive effect which is based on crystalline thin films. Therefore, if an amorphous thin film combining room temperature ferromagnetism with transparency and semiconductor behavior can be found, it has the potential for immediate impact on spintronic technologies.
Among available amorphous oxide semiconductor materials, very few have shown the ability to transport current using electrons (i.e. n-type) as well as by holes (i.e. p-type. Having a semiconductor material that can show both n- and p-type behaviors makes them candidates for monolithic semiconductor devices, such as the Silicon based technologies. Furthermore, an amorphous oxide semiconductor shown in both n- and p-type makes it feasible to achieve all amorphous oxide electronics. Such a material could help reduce the cost of computer and display technologies.
Terfenol-D is a well-known metal alloy having a cubic crystalline microstructure, often defined by the formula TbxDy1-xFe2 where x≈0.3; Terfenol-D is also often defined as having a stoichiometry of TbxDy1-xFey where x≈0.3 and y≈2.0. Therefore, Terfenol-D is known to generally consist of about 66.67 atomic percent iron, about 23.33 atomic percent dysprosium, and about 10 atomic percent terbium. Stoichiometry of Terfenol-D has been measured and found to be Tb0.27Dy0.73Fe1.95, which translates to 65 atomic percent iron, about 24 atomic percent dysprosium, and about 9 atomic percent terbium.
Terfenol-D is known to have the highest magnetostriction of any alloy, up to 0.002 m/m at saturation, and was developed for use in naval sonar systems. Terfenol-D is also used in magnetomechanical sensors, actuators, and acoustic and ultrasonic transducers, and the like.